We went early September and was a great trip. Murano was a bit rushed. By the time you have looked round the glass shop not time for anything else. Burano was fantastic and could have had 30-60 mins longer. Torcello - well it is deserted - so not our cup of tea really.
One of the best trips we have done. We were actually in a group of six and the headsets are really good so you hear everything. Water taxi ride and the walk were really informative, right length and we would recommend to everyone.